HR: 16:20h
AN: S12E-02    [PDF]
TI: Challenges in Seismic Hazard Mapping of the Great Basin
AU: * Petersen, M D
EM: mpetersen@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center, MS 966, Box 25046, Denver, CO 80225 United States
AU: Frankel, A D
EM: afrankel@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center, MS 966, Box 25046, Denver, CO 80225 United States
AU: Cramer, C H
EM: cramer@usgs.gov
AF: U.S. Geological Survey, 3876 Central Ave., Suite 2, Memphis, TN 38152 United States
AB: The Great Basin has hundreds of seismically active faults. Most of these earthquake sources have low to moderate slip rates, and only rupture in large earthquakes every few thousand to tens of thousands of years. In spite of these low activity rates several faults have generated large earthquakes; ten earthquakes have ruptured the surface during the past two centuries, and several of those ruptures are attributable to faults that did not have evidence of Holocene displacement. The large number and vast areal extent of these faults cause a significant hazard that must be considered in engineering, emergency response planning, and other public policy applications. We recently updated the USGS National Seismic Hazard Maps which are now available on the USGS website (http://geohazards.cr.usgs.gov/eq/). This update involved reassessment of fault slip rates, magnitudes, magnitude-frequency distributions, geodetic data, and attenuation relations. Several issues are being evaluated for future versions of these maps: (1) Alternative source models: We compare the hazard calculated using an alternative multi-segment rupture model for the Wasatch fault with the individual segment rupture models that were used in the 2002 update. (2) Alternative recurrence models: Time-dependent hazard at sites along the Wasatch front have been calculated using the Brownian Passage Time recurrence distribution. This distribution is characterized by mean recurrence and aperiodicity that are computed from the paleoseismic data. Geodetic data was evaluated to analyze strain rates across the Great Basin and influenced modeling of the Central Nevada Seismic Zone. (3) Updated attenuation relations: Current studies are focusing on the attenuation properties of the crust across the Great Basin. (4) Monte Carlo uncertainty analysis: We have calculated uncertainty for the hazard at several sites by varying the characteristic magnitude, fault slip rate or recurrence rate, fault length, magnitude-frequency distributions, and attenuation relations. This uncertainty is about +/- 50% of the mean value at one standard deviation. (5) Urban hazard maps: We have begun collecting data along the Wasatch fault to develop a community 3-D velocity model. Evaluation of these important issues by working groups from the Earth-science and engineering communities will lead to products that incorporate the best science available and that are useful for public policy applications.
UR: http://geohazards.cr.usgs.gov/eq/
DE: 7212 Earthquake ground motions and engineering
DE: 7221 Paleoseismology
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting